1. Technical Field of the Invention
The present invention relates to polymer coatings or varnishes capable of conferring resistance to soiling on supports which may be at least partially composed of silicone.
The support substrates concerned are various and can, in particular, be composed:
of flexible supports, in particular fibrous supports, which may or may not be woven, coated with at least one layer for mechanical strengthening or protection based on the coating polymer, for example of the silicone elastomer type;
of supports in the massive form made of silicone and/or coated with one or more silicone layers, for example components made of metal, of plastic or ceramic (composite components, such as electrical insulators, e.g.,);
or else of polymer or elastomer supports, in particular plastic films, such as, for example, protective packaging films.
The present invention also relates to processes for the application to various supports of an anti-soil varnish.
Too, this invention relates to supports coated with such anti-soil varnishes and in particular flexible supports, such as textile cloths optionally coated with a layer of silicone elastomer, the anti-soil varnish being applied to the layer of silicone elastomer, such cloths being useful for the manufacture:
1. of architectural textiles (components of textile architecture);
2. or else of flexible supports other than architectural textiles.
As regards the field of application 1., it should be appreciated that, throughout the present account and within the meaning of the present invention, the term “architectural textile” means a woven fabric or nonwoven fabric and more generally in the fibrous support intended, after coating, for the preparation:
of shelters, of mobile structures, of textile constructions, of partitions, of flexible doors, of tarpaulins, of tents, of stands or of marquees;
of furniture, of cladding, of advertising displays, of windbreaks or of filter panels;
of solar protection devices, of ceilings and of blinds.
As regards the field of application 2., it will be appreciated that these flexible supports other than architectural textiles can, for example, be those intended for the manufacture, of in particular:
airbags used for the protection of the occupants of a vehicle,
glass braids (woven glass sheaths for thermal and dielectric protection for electrical wires),
conveyor belts, fire barrier fabrics or thermal insulation fabrics,
clothes,
compensators (flexible sealing sleeves for pipe work).
Silicone elastomer coatings on textile supports, due to the intrinsic properties of silicones, already impart numerous advantages on the composites thus formed, namely, inter alia:
flexibility,
mechanical strength,
thermal stability,
release properties,
and longevity.
However, in the field of textile architecture, which constitutes an important application for the above said composites, other requirements have been formulated, which are in particular the following:
resistance to soiling substances,
good characteristics with regard to appearance,
especially with respect to the coloring and the gloss,
ability to adhesively bond, to make it possible to easily assemble the composites two by two,
low sliding coefficient in order to favor the handling of the composite,
good cohesion of the composite.
These properties can be provided by an appropriate surface coating. The general problem and the basis of the invention is thus the development of a silicone varnish capable of fulfilling this role, in particular as regards the anti-soil properties.
However, before satisfying the requirements relating to the final applications targeted for the composite, it is important for this varnish to furthermore meet upstream specifications, namely, in particular:
to be able to be easily spread over a silicone layer, indeed even a nonsilicone layer (for example polyvinyl chloride, polyurethane or polyamide),
to adhere perfectly to this silicone or nonsilicone layer,
and more generally to be easy and economical to employ industrially.
2. Description of Background and/or Related and/or Prior Art
WO-A-00/59992 discloses silicone compositions for use in particular for the preparation of varnishes which can be applied to supports for which it is desired to reduce the coefficient of friction. One of these compositions comprises at least one polyorganosiloxane A (POS) which can be crosslinked via crosslinking functional groups (CFGs) by the cationic and/or radical route and an initiator C selected from among onium borates, wherein it additionally comprises POS D molecules substituted by secondary functional groups (SFGs) carried by silicon atoms and selected from those comprising at least one alkoxy and/or epoxy and/or carboxyl unit, and optionally a filler (e.g., silica).

These compositions can additionally comprise fillers and in particular siliceous fillers, which can, for example, be:
combustion or pyrogenic silicas treated with hexamethyldisilazane or with octamethylcyclotetrasiloxane (specific surface up to approximately 300 m2/g), fumed silicas, ground synthetic or natural fibers (polymers), calcium carbonates, talc, clays, titanium dioxides, and the like.
Such compositions are used as anti-soil varnishes for RTV silicone coatings of fabrics for air bags, for thermal transfer ribbons or for packaging films.
Such varnishes are not the most effective in terms of anti-soil properties and can be improved in terms of sliding coefficient. In addition, they require the use of specific silicones which can be crosslinked by cationic routes under UV activation, which leaves a margin for improvement economically and with regard to simplifying the means employed.
It is thus apparent that the prior art is essentially devoid of anti-soil varnishes compatible with coatings, in particular silicone elastomer coatings, for supports, in particular textile supports, and even less in anti-soil varnishes which meet the above specifications.